The goal of this project is to provide statistical and computational expertise in the design, analysis, and interpretation of experimental results for a variety of Institute research activities, including both laboratory and human studies. Approximately 80 scientists made use of the Statistical Consulting Service in FY99. Many of these activities involved NTPs long term rodent carcinogenicity studies. During FY99 we provided significant input into the preparation of approximately 12 NTP Technical Reports that summarized the results of these studies. We also coauthored papers in the scientific literature dealing with the carcinogenic effects of magnetic fields, ethylbenzene, pentachlorophenol, and molybdenum trioxide. Examples of other collaborations include an assessment of the proliferative target organ effects and control tumor profiles observed in a set of NTP studies in Tg.AC transgenic and p53-heterozygous mice, two genetically altered mouse strains which are of emerging importance in toxicologic pathology. - Statistical consulting; collaborative research; experimental design; data analysis; National Toxicology Program